Artificial denture

ABSTRACT

A denture is constructed with molars in a first denture base having flat chewing surfaces in a common plane. Elongated ridges on opposing molars in a second denture base provide a biting edge which makes continuous linear contact in centric occlusion with the flat surfaces in the same common plane. The plane passes through upper portions of the retromolar pads and the incisal edges of the central incisors, and is also substantially parallel to a line passing through the hamular notches. Parallel transverse ridges on the upper first or second bicuspids engage the lower posterior biting edge in protrusive movement to keep the denture bases seated.

United States Patent Feb. 1, 1972 Frush [54] ARTIFICIAL DENTURE [72]Inventor: John P. Frush, 704 Highland Drive,

Pasadena, Calif. 91 108 [22] Filed: Jan. 29, 1970 [2|] Appl. No.: 6,904

[52] US. Cl ..32/2 [5 1] Int. Cl r ..A6lc 13/00 [58] Field of Search..32/8, 2

[56] References Cited UNITED STATES PATENTS 2,669,021 2/1954 Bader..32/2 2,617,192 11/1952 Goddard... ...32/2

Beresin Primary Examiner-Robert Peshock Attorney-Christie, Parker & Hale[57] ABSTRACT A denture is constructed with molars in a first denturebase having flat chewing surfaces in a common plane. Elongated ridges onopposing molars in a second denture base provide a biting edge whichmakes continuous linear contact in centric occlusion with the flatsurfaces in the same common plane. The plane passes through upperportions of the retromolar pads and the incisal edges of the centralincisors, and is also substantially parallel to a line passing throughthe hamular notches. Parallel transverse ridges on the upper first orsecond bicuspids engage the lower posterior biting edge in protrusivemovement to keep the denture bases seated.

16 Claims, 5 Drawing Figures PATENTEU H51 1972 I 3338.309

SHEET 1 BF 2 INVENTOR. JOHN P, FRUSH Maw/M A TTORNE V5 ARTIFICIALDENTURE This invention relates to dentures made with artificial teeth.

Many of the prior art dentures use artificial teeth made to approximatethe sizes and shape of natural teeth, and they are somewhat difficult toshape and form. More important, the irregular masticating or crushingsurfaces of the prior art teeth present valleys or troughs which areengaged by projections from the crushing surfaces of opposing teeth, andcause locking or bumping of the teeth or dentures. These irregularitiesin the opposing surfaces of the teeth create cusp rise or occlusaldeflections which tend to shift the dentures on the ridges of thepatients mouth during mastication or sliding movements of the mandible.This makes the denture uncomfortable and unsatisfactory for efficientcrushing of food. In addition, many of the prior art teeth are shaped sothat perfect mounting must be achieved to obtain proper crushing. Theprior art teeth also require fairly high biting pressures to achieve thedesired cutting and crushing effect in chewing. For these reasons, theartificial teeth of the prior art, even when accurately positionedrelative to the other teeth in the mouth, cannot prevent undesirablepressure from being transmitted through the teeth to the gums andcausing sore spots and sensitive areas which are painful to the patient.People are also prevented from having a normal variety of food whichrequires these pressures for mastication.

The chewing or crushing motion in a human being is a fairly complexmovement about three mutually perpendicular axes, plus a fourth axisparallel to one of the three. The lower jaw or mandible can move up anddown about a horizontal axis which extends from left to rightapproximately through the condyles of the lower jaw. The mandible canpivot about either a right or a left sagittal (fore and aft) axis whichextends horizontally through each condyle of the lower jaw. The mandiblecan also move laterally around a vertical axis which extends verticallythrough the condyle. When the mandible shifts laterally, the side movinginwardly drops slightly about the sagittal axis on the opposite side,and the side moving outwardly drops slightly, or not at all. This typeof movement makes it difficult for a patient wearing prior art denturesto maintain uniform chewing or cutting contact between the teeth withoutirritating movement of the dentures and without a degree of discomfort.This invention provides in its preferred form opposing teeth with linearor blade contact to modify this movement about the sagittal axis and toprovide less interference in the contacting surfaces when the mandiblemoves away from center position.

Briefly, this invention provides an improved prosthodontic masticatorysystem for endentulous patients. A lower denture base rests on the gumtissue overlying the mandible of the patient. An upper denture basebears against the gum tissue covering the maxilla (upper jaw bone) ofthe patient. One of the denture bases includes at least one elongatedportion having a flat surface facing the other denture. The flat surfaceextends over an area substantially corresponding to that previouslycovered by at least the first and second adjacent natural molars of thepatient. The other denture base includes an elongated ridge whichextends for a distance at least equal to that previously covered by thespan between the mesial edge of the first molar and the distal edge ofthe adjacent second molar. The ridge projects toward the flat surface toform a biting edge which lies in substantially the same plane as theflat surface when the denture bases are held in centric contact.

Preferably, the upper denture includes a pair of flat surfaces lying ina common plane. Each flat surface covers an area corresponding to atleast the first and second upper molars on each side of the patientsmouth. The lower base carries a pair of laterally spaced ridges each ofwhich is adapted to bear against a respective flat surface on the upperdenture base.

Preferably, the common plane in which the biting edges bear against theflat surface when the dentures are held in centric contact passesthrough upper portions of the retromolar pads in the patients mouth andthrough the incisal edges of the upper central incisors mounted in theupper denture base. The common plane is preferably parallel to thetransverse axis of the temperomandibular joints of the patient. Thisaxis is difficult to determine in a patient, but a close approximationis made by having the plane substantially parallel to a line passingthrough the hamular notches in the patients mouth.

To prevent the denture bases from tending to becomes unseated when thepatient slides his mandible forward in a protrusive position, atransverse ridge is provided on each of the first or second bicuspids inthe upper denture base which also includes the flat surfaces. Thus, asthe mandible slides forward, the biting edge opposing the flat surfacestends to slide across the transverse ridges on the bicuspids. This keepsthe anterior teeth from contacting and tending to pivot the denturesinwardly about axes passing through the anterior ridges of the mandibleand the maxilla. To facilitate this function, the incisal edges of thelower anterior teeth are spaced slightly below the plane of contactbetween the biting edges and flat surfaces so that the upper and loweranterior teeth do not intercept when the mandible is moved toward theprotrusive position.

These and other aspects of the invention will be more fully understoodfrom the following detailed description and the accompanying drawings inwhich:

FIG. I is a schematic side elevation showing the masticatory system ofthis invention mounted in the patients mouth;

FIG. 2 is a view taken on line 2-2 of FIG. 1;

FIG. 3 is a schematic side elevation of the dentures with the mandiblein the protrusive position;

FIG. 4 is a view taken on line 4-4 of FIG. 1; and

FIG. 5 is a perspective view of the lower denture made in accordancewith this invention.

Referring to FIG. 1, the prosthodontic masticatory system 10 of thisinvention includes a lower denture base 11 adapted to fit over and reston the mandibular ridge 12. An upper denture base 14 is adapted to seaton and bear against the maxillary ridge 16. Each base is made ofconventional denture plastics and is generally horseshoe shaped in planview as shown best for the lower base in FIG. 5. Each base also includesa generally U-shaped groove 18 (FIG. 2) opening away from the opposingdenture base so as to seat on and grip the mandibulary or maxillaryridge.

Referringto FIGS. 1 and 5, the lower denture includes the followingartificial teeth mounted in and projecting upwardly from the uppersurface of the lower denture base:

Right and left lower central incisors 20, right and left lower lateralincisors 21, right and left lower cuspids 22, right and left lower firstbicuspids 23, right and left lower second bicuspids 24, right and leftlower first molars 2S, and right and left lower second molars 26. Thesix anterior artificial teeth in each denture are shaped and colored toappear like natural teeth. The eight posterior teeth are colored andgenerally shaped like natural teeth except for the occlusal surfaces 28(FIG. 2). The buccal edge of each lower posterior tooth carries alongitudinally and upwardly extending ridge 29 which terminates in arelatively sharp biting edge 30. Preferably, the right lower posteriorteeth are cast form plastic or the like in an integral block which isshaped to look like four separate teeth. The same is true for the fourposterior teeth on the left side of the lower denture. Preferably, eachbiting edge 30 for each of the sets of four posterior teeth iscontinuous to form an elongated and substantially linear cutting edge.The upper surface of each lower posterior tooth slopes downwardly andinwardly in a gentle upwardly concave curve to form a lower crushing ormasticating surface 31. Each lower posterior tooth also slopes outwardlyand downwardly in a relatively steep convex curve to form the buccalside 32 of the tooth. The biting edges 30 on each set of four posteriorteeth lie in a common flat plane.

Referring to FIGS. 1 and 4, the upper denture includes the followingartificial teeth mounted in and projecting downwardly from the lowersurface of the upper denture base:

Right and left upper central incisors 34, right and left upper lateralincisors 36, right and left upper cuspids 38, right and left upper firstbicuspids 39, right and left upper second bicuspids 40, right and leftupper first molars 42, and right and left upper second molars 43.

In the preferred form of the invention, each set of four posteriorartificial teeth on each side of both the upper and lower bases are castfrom porcelain or plastic as an integral and continuous unit. Forexample, the occlusal surfaces 50 on the upper posterior teeth are castto lie in a common flat plane, and are set on a flat plate or template(not shown), which establishes that plane. The same is true of thebiting edges of the lower posterior teeth. An inwardly extendingstabilizing bar 51 is formed integrally with each set of upper posteriorteeth and rests on the template to stabilize the teeth in the properposition on the template while the teeth are set in the upper denturewax base. Thereafter, the stabilizing bars are removed, say by cutting.The stabilizing bar can be separate as shown in FIG. 4, or can be joinedtogether at their inner portions. It can be fixed to the teeth orseparate, fitting into slots formed in the occlusal surfaces to receivesame.

As shown best in FIG. 1, when the mandible 52 is in the centric positionwith respect to the maxilla 54, the biting edges 30 of the lowerposterior teeth bear against the flat surfaces of the upper posteriorteeth in a common flat intermaxillary plane 56 (shown in phantom line)which passes through the line of contact of the biting edges 30 of thelower posteriors and the flat surfaces 50 of the upper posteriors.Preferably, the intermaxillary plane also passes through the upperportions of the retromolar pads 58 (shown in phantom line) and theincisal edges of the upper central incisors 34. The intermaxillary planeis also preferably parallel to a line (not shown) passing through thehamular notches 60 in the patients mouth.

The lower anterior teeth are placed in the lower denture so that theyare spaced slightly, preferably about 0.020 inch, below theintermaxillary plane as shown in FIG. 1, when the dentures are incentric contact.

A separate downwardly facing transverse fulcrum ridge 62 (FIGS. 1, 3,and 4) is formed across the flat surface of each of the first bicuspids.The ridges on the bicuspids are parallel, preferably collinear, and theylie in the intermaxillary plane 56. The ridges provide a fulcrum ofstability when the mandible is moved forward to the protrusive positionshown in FIG. 3. The fulcrum ridges on the first or second bicuspids andthe location of the lower anteriors below the intermaxillary planepermit the mandible to slide forward into the protrusive position shownin FIG. 3 without developing any unseating forces on the dentures, asexplained more fully below. The transverse fulcrum ridges 62 can belocated on the second bicuspids instead of the first bicuspids. This hasthe advantage of providing a seating force which is more centrallylocated than that provided with the transverse ridges on the firstbicuspids. If the ridges are on the second bicuspids, the firstbicuspids become substantially nonfunctional. This is not a seriousdisadvantage because most of the chewing is provided by contact betweenthe first molars and second bicuspids of the upper and lower sets ofteeth.

The advantage of the dentures of this invention will be more completelyunderstood from the following description with reference to FIGS. 1 and2 which show schematically how the mandibular condyles 70 fit into theglenoid fossae 72 of the temporal bone to form the temporal mandibularjoint 74 in which the mandible is hinged to the maxilla.

In the following description, the term intermaxillary planar contactmeans that every contact between the upper and lower denture masses,regardless of the position of the mandible,is within a common plane,which for the purpose of this invention is referred to as theintermaxillary plane. Since the intermaxillary plane is flat, thedenture masses are noninterceptive, i.e., there is an absence of anymechanical projection in the occlusion, or any part of the denture basewhich would intercept single plane contact due to movement of thedentures relative to each other.

People who wear dentures which do not include the present inventionexperience three main problems, namely:

1. Discomfort 2. Inability to chew various foods, and

3. Looseness of the dentures. Pain and discomfort force most patients toleave their lower denture out either all or part of the time. Inabilityto chew various types of food often forces patients to restrict theirdiet. Looseness of the dentures often makes it necessary to employadhesive powders and to endure the flow of food under the dentures whileeating a meal.

The dentures of this invention improve the standard of performance ofartificial dentures by correcting the main factor which causes the abovethree problems. The main factor causing tipping, looseness, anddiscomfort with dentures is movement of the denture bases on thedenture-supporting gum tissue (cornified oral mucosa) when the upper andlower dentures make contact. The construction of the dentures of thisinvention stabilizes the upper and lower dentures of this invention onthe tissue, and thus provides new and improved conditions for comfortand health of the gum tissue. This result is obtained because theocclusal surfaces 50 of all the upper posterior teeth are in a flatplane, and the biting edges 30 of the lower posterior teeth are also ina flat plane. Moreover, the dentures are constructed so that allocclusion between them occurs in a common plane at a fixed positionregardless of the position of the mandible. Since the plane is flat, allocclusion is therefore noninterceptive, i.e., occlusion takes place insuch a way that the dentures tend to remain seated rather than be tippedand become unseated. Also, all forces and counterforces of occlusalcontact are vertical to the ridges (see arrows, FIG. 2).

The noninterceptive environment during intermaxillary denture contactreleases the condyles of the temperomandibular joint from the variousand confused neuromuscular stimuli which result from interceptivecontacts of dentures not employing this invention.

The intermaxillary planar contact and the transverse ridges on the firstbicuspids provide a noninterceptive intermaxillary contact whichdecreases or eliminates the need in the joints for the classicmandibular sagittal, vertical and transverse rotations required toaccommodate the slanted contacting and intercepting surfaces, as in theconventional dentures. All contacts between upper and lower teeth ofdentures prior to this invention have been referred to as various typesof occlusion," the posterior teeth being set in different planes ofcontact, which have created transverse forces, i.e., forces which tendto unseat the dentures, that cause movement of the dentures on the gumtissue.

The dentures of this invention create the noninterceptive environmentwhich permits lateral movements of the mandible without the transverseunseating forces of the dentures. This occurs because all contactsbetween the anterior and posterior teeth of the upper and lower denturesin every jaw position is of linear origin and occurs in theintermaxillary plane established as described above. In making thedentures of my invention, the intermaxillary plane is established,controlled, and maintained in the upper denture. When proper verticaldimension is supplied, the linear-plane contact allows the condyles tomove freely in their glenoid fossae and in a way which allows bilateralbalancing without cusp rise during a lateral shift of the mandible. Thisfunction has not been previously obtained with prior dentures becausethe proper noninterceptive environment for the phenomenon has not beensupplied.

The proprioceptive nervous system stimulates hyperactive condylemovement which is an accommodation for multiplanar denture contacts,such as occur with dentures prior to this invention. With linear contactin a single plane provided by this invention, the proprioceptiveinfluence on excessive condyle movement is suppressed. This allows thecondyles freedom of movement within the fossae. Since the single flatintermaxillary plane of contact influences the pattern of mandibularmovement so consistently, I refer to this phenomenon as environmentalgnathology.

The precise contact between the denture masses within the flatintermaxillary plane 56 properly oriented with respect to the craniumproduces maximum benefit to the patient in comfort, chewing, andstability because linear contact, properly oriented in a single plane,results in comfortable seating forces which hold the denture basesstable and virtually unmoving during any. contact between the dentures.The usual tilting, tipping, and sliding movements of prior dentures ,onthe underlying gum tissue is thus minimized. The denture-supporting gumtissue contains proprioceptive nerve endings which respond to thestimuli of denture movement. These stimuli influence the pattern ofmandibular movement, condyle position, and the comfort of the entiretemperomandibular joint. when the stimuli induced by the movementof the.denture base on the supporting 'tissueare suppressed by-the dentures ofthis invention, the proprioceptive nerve endings are not activated tochange mandibular movement as a'preventative of tissue injury. Theproprioceptivenerve, system is a protective mechanism which interceptany-mandibular movement, when artificial teeth touch, whichwouldinju'refthe.tissue .if such movement continued. Such injury wouldbe caused by subsequent traumatic movement of the relatively harddenture base on the sensitive gum tissue. Thus, by stabilizing thedentures on the gum tissue through the linear single plane contactbetween the upper and lower dentures, instead of multiple planes ofocclusal contact between individual opposing teeth as with priordentures, a superior and unique masticatory system is provided for thepatient.

As stated above, the location of the flat intermaxillary plane 56 isdetermined by the incisal edge of the upper artificial central incisors34 and the patients retromolar pads 58 (upper portion). The position ofthe intermaxillary plane of contact between the dentures is thereforerelated to:

l. Anatomic guides provided by the patient (the retromolar pads), and

2. The aesthetic position of the upper central incisor teeth asdetermined by he dentist or technician. The intermaxillary plane 56 isalso established to be parallel to the axis passing through themandibular condyles. Since this is difficult to obtain directly from thepatient, a good approximation of the direction of the axis isaccomplished by making a wax rim on the conventional upper cast whoseinferior surface is horizontally parallel to a line passing through themaxillary hamular notches 60. Thus, the upper wax rim accomplishes twofunctional requirements incidental to the establishment of theintermaxillary plane. It is used essentially as the height of the planarcontact in the anterior region and it establishes the horizontal levelof the planar contact by paralleling it with the hamular notches, whichare used as a bench mark because they are readily available onendentulous upper casts, and they are essentially parallel to the axispassing through the mandibular condyles. The intermaxillary plane ofcontact is made parallel to the transverse axis of the condyles 70 bythe use of a flat metal template (not shown) preferably 0.020 inchthick. The template is placed on the lower mounted cast at theretromolar pads 58 in back, and is supported by a softened wax rim,adapted to the lower ridge in front.

As stated above, the mandibular condyles 70 are where the mandible ishinged to the cranium, and are the source of all mandibular movement.Thus, the intermaxillary plane 56 should be parallel to the axis passingthrough the mandibular condyles. Since a line passing through the sameportions of the hamular. notches 60 is substantially parallel to thetransverse axis of the condyles in the glenoid fossae, the plane ofcontact is made essentially substantially parallel to the transverseaxis of the condyles by having it parallel to a line passing through thehamular notches.

It is important for the intermaxillary plane 56 to be parallel to thetransverse axis of the mandibular condyles 70 to insure tioning integralunit. A movement in one part of the mass produces movement inanotherpart of the same mass. Therefore, it is. necessary to realize thatthemovement of an individual creates a movement of the entire denture mass.If the intermaxillary plane of contact is not substantially parallel-tothe transverse axis passing through the condyles, the upper dentureocclusion actsas one large cusp incline. For example, if theintermaxillary plane of contact were'not parallel to. the transverseaxis, passing through the condyles, a lateral shift of the'mandiblewould cause it to move up or down, depending on the direction oftransverse inclination of intermaxillary plane, and transversedenture-unseating forces would develop as the dentures move on theridges. This change in the vertical -p'osition of planar contact wouldact as a cusp rise because it would change the vertical distance betweenthe upper and lower jaws. It does not make any difference whether thischange is caused-by cusp rise on individual teeth in the dentures, or bythe denture mass itself. In either instance, transverse forces arecreated which cause denture base movement. This would stimulate theproprioceptive nervous system ,to protect the tissue from the resultingtraumatic movement of-the denture bases, and would, thus, reinstate the-classic pattern of condyle movements required when the teeth contact indifferent planes (asin prior art dentures) to achieve balancedocclusion. The properly oriented flat intermaxillary plane of contactprovided by these dentures provides the necessary environment forsimplified action of the condyles in their fossae.

The dentures of this invention are particularly useful in overcoming oneof the major difficulties which has consistently interfered with denturebase stability when the patient slides his mandible intoaprotrusiveposition such as that shown in FIG. 3. In the protrusive position, thecondyles 70...

move out of the fossae 72 in a transitional movement, forward anddownward on the eminencae in front of the glenoid fossae. As thecondyles move forward and downward, the mandible on which the lowerdenture rests drops in its posterior region and usually separates theteeth in the posterior part of the denture so that the forces of contactare transmitted immediately to the front teeth. In artificial denturesthe front teeth are traditionally placed ahead of the anterior portionsof the maxillary and mandibular ridges and, therefore, when the frontteeth make contact, the interior portions of the ridges act as fulcrums.The anterior teeth become the force, an the denture bases behind theanterior ridges are levered toward each other and dislodged in back.Dentures prior to this invention have tried to compensate for thiseffect, but the resultant curves and cusp rise in the occlusion hasalways produced transverse unseating forces instead of stabilizingseating forces produced by the dentures of this invention.

The unseating forces produced by dentures prior to this invention notonly act as stimuli to proprioceptive activity involving environmentalcompensating adjustment of the condyles, but also produce traumaticmovements and pressures of the denture bases against the sensitive gumtissues. The interdenture contact provided by this invention establishesvertical seating forces within the dental arch rather than thetransverse unseating forces outside the dental arch in protrusive'movement. The seating forces are established with the dentures of thisinvention in the upper first or second bicuspids by creating a fulcrum(the transverse ridges 62 on the bicuspids) for the biting edge of theblade of the lower denture to ride on in As the biting edges 30 of thelower posterior teeth slide forward in the mouth in a protrusivemovement, they ride on the bilateral fulcrums of stability (thetransverse ridges 62 on the bicuspids), which provide the only contactbetween the denture masses. The mandible 52, therefore, rotates about atransverse horizontal axis on these fulcrums, providing denture seatingforces behind the anterior ridges of the maxilla and mandible. Thispressure behind the anterior arch provides a vertical stabilizing orseating force (FIG. 3) instead of unseating force, as experienced inprevious dentures.

With the dentures of this invention, the lower anterior teeth rise in aprotrusive movement ahead of the fulcrum as the lower posterior teethdrop behind the fulcrum. Thus, it can be seen why, to createnoninterceptive inter-maxillary contact during mandibular movements inthe protrusive, the lower anterior teeth are positioned below theintermaxillary plane of contact in the prefabricated block of teeth.

Preferably, the biting edges of the first and second bicuspids in thelower denture are continuous, and do not contain any interruptions ornotches between these teeth which would tend to engage the fulcrums,causing a bump in the protrusive slide. This bumping would not onlyincrease proprioceptive activity, but could traumatize the gum tissueunderneath the denture by creating transverse forces at the moment ofthe contact of the notches with the fulcrum. The continuous blade on thelower bicuspids permits the lower denture to slide uninterruptedly alongthe fulcrum. Consequently, the biting edge of the ridge or blade on thelower first and second bicuspids is preferably continuous. Thus, in aprotrusive movement of the mandible, the lower denture is seatedbilaterally and evenly in the mouth by the fulcrums on the two upperbicuspids in a continuous, smooth, noninterceptive manner.

The artificial teeth used in the dentures of this invention can bemanufactured to include all of the teeth or just the posterior teeth.They can be a one-piece plastic mold, or a combination of plastic andporcelain teeth, or made up totally of porcelain teeth attached to eachother by any suitable means which insures that the flat surfaces of theupper posterior teeth are in the same common plane and that the bitingedges of the upper central incisors are in the same common plane andthat the lateral incisors and cuspids are above this same plane. Thebilateral fulcrum of stability may be manufactured in either the firstor the second bicuspids. The bilateral fulcrum is preferably placed inthe second bicuspids. This moves the horizontal axis of rotation of themandible in a protrusive movement more to the center of that part of theupper ridge which runs antero-posteriorly. The first bicuspids are thenplaced above the intermaxillary plane of contact in the manufacture ofthe teeth. In doing so, every means can be used to create the bestaesthetic form of the first bicuspids since their functional roll isremoved.

A lower prefabricated arch of teeth is correlated to each upperprefabricated arch. In the preferred form of the invention, the upperposterior teeth have the flat surfaces, and the lower posterior teethcarry the biting edges which bear against the flat surfaces of the upperposteriors. However, the positions of the flat surfaces and biting edgescan be reversed in the upper and lower dentures as long as the occlusalsurfaces of the dentures meet in a common intermaxillary plane asdefined above.

The biting edges and the flat surfaces can be reversed from thepreferred arrangement to provide a cross-bite for certain anomalouscases, e.g., a class III prognathic relationship. How ever, it isdesirable for the upper posterior teeth to have the fiat surface, andthe biting edge to be at the buccal side of the lower teeth as shown inFIG. 2. With this arrangement, the upper teeth hold the cheeks of thepatient away from contact between the upper and lower posteriors, andthus reduce the tendency for the patient to bite his cheek. Moreover,with the biting edge at the buccal side of the posterior lower teeth,the cut portions of food being chewed tend to move toward the patientstongue rather than being caught between the patients cheek and teeth.The movement of the out food toward the patients tongue also facilitatesfurther mastication between the lingual side of the flat surfaces andthe concave portions of the posterior teeth below the plane of contact.Finally, the location of the flat surfaces on the upper posteriorspermit them to be arranged in the position shown in FIG. 2 to encouragebits of food to move inwardly rather than toward the cheeks. Thearrangement of FIG. 2 also has the advantage that it more nearlysimulates the appearance and arrangement of natural teeth, and thus isaesthetically preferable.

With the upper and lower denture teeth prefabricated and mounted asdescribed above, the aesthetics are excellent. A unique relationship ofthe dentures of this invention in the centric position is that theincisal edges of the upper central incisor teeth are in theitermaxillary plane of contact, while the incisal edges of all the loweranterior teeth are located below the plane of contact. The opposite hasbeen traditional with dentures prior to this invention. That is, theanterior teeth usually overlap, and this is generally called anoverbite." The dentures of this invention permit the teeth to be mountedas shown in FIG. 1 and described above, and, Le, there is an underbiteof the anterior teeth, and it is prefabricated in the manufacture of thedenture teeth.

THe various structures of artificial denture teeth described hereinpermit a prefabricated assembly of upper and lower dental arches invarious aesthetic tooth forms and sizes which accelerate the productionof dentures in the laboratory. The traditional methods used prior tothis invention required assembling each tooth individually in wax rims,positioning one tooth next to the other, and then, in functionalrelationship with the teeth of the opposite arch set in a similar way.This invention precludes the necessity of handling teeth individuallyand allows a unit assembly of each dental arch between the casts on asingle plane of contact. This plane of contact is related consistentlyand accurately to the patients anatomic landmarks which providenoninterceptive movements of the dentures.

What is claimed is:

l. A prosthodontic masticatory system for an edentulous patient, thesystem comprising a lower denture base adapted to rest on the gum tissueoverlying the mandible of the patient, and an upper denture base adaptedto bear against the gum tissue covering the maxilla of the patient, oneof the denture bases inclu;ing at least one elongated portion having aflat surface facing the other denture and extending over an areasubstantially corresponding to that previously covered by at least thefirst and second natural molars, the other denture base including anelongated ridge extending for a distance at least equal to thatpreviously covered by the span between the mesial edge of the firstmolar and the distal edge of the second molar, the ridge projectingtoward the said flat surface to form a biting edge which lies insubstantially the same plane as the flat surface when the denture basesare held in centric contact.

2. A system according to claim 1 which includes a first flat surface onone side of one of the denture bases, and a second flat surface on theopposite side of the denture facing the other denture, the first andsecond fiat surfaces lying in a common flat plane, and a transverseridge adjacent to each of the fiat surfaces and extending toward theother denture base, each transverse ridge lying within the spacepreviously occupied by the natural bicuspid teeth of the patient, andlaterally spaced elongated ridges on the said other denture eachprojected toward a respective flat surface to form biting edges whichlie in substantially the same plane as the flat surface when the denturebases are held in centric contact.

3. A system according to claim 2 in which the two flat surfaces are onthe upper denture, and the biting edges are on the lower denture.

4. A prosthodontic masticatory system for an edentulous patient, thesystem comprising a lower denture base adapted to rest on the gum tissueoverlying the mandible of the patient, and an upper denture base adaptedto bear against the gum tissue overlying the maxilla of the patient, oneof the denture bases including a pair of elongated, laterally spacedsubstantially continuous flat surfaces lying in a common plane facingthe other denture base, each flat surface being disposed over an areasubstantially corresponding to that previously covered by at least thefirst and second natural molars on a respective side of the mouth of thepatient, the other denture base including a pair of substantiallycontinuous elongated laterally.

spaced. flat ridges lying substantially in the common plane, each ridgeextending for a distance substantially equal to that previously coveredby at least the first and second natural molars on a respective side ofthe mouth of the patient.

5. A system according to claim 4 in which the common plane issubstantially parallel to a transverse axis passing through thetemperomandibular joint of the patient.

6: A system according to claim 5 in which the common plane passessubstantially through the incisal edge of the upper central incisorteeth of the upper denture.

7. A system according to claim 5 in which the common plane passesthrough the upper portion of the retromolar pads of the patient.

8. A system according to claim 6 in which the common plane passesthrough the upper portion of the retromolar pads.

9. A system according to claim 4 in which the denture base with the flatsurfaces includes a downwardly facing transverse fulcrum on each side ofthe said denture, each fulcrum being located within the space previouslyoccupied by the bicuspid teeth of the patient.

10. A system according to claim 4 in which the incisal edges of thelower central incisors are spaced below the common plane.

11. A system according to claim 10 in which the lower central incisorsare behind the upper central incisors to form an underbite.

12. The system according to claim 4 in which each ridge also extends fora distance substantially equal to that previously occupied by thebicuspid teeth of the patient.

13. A prosthodontic masticatory system for an edentulous patient, thesystem comprising a lower denture base adapted to rest on the gum tissueoverlying the mandible of the patient, and an upper denture base adaptedto bear against the gum tissue overlying the maxilla of the patient, oneof the denture bases including a pair of elongated, laterally spacedflat surfaces lying in a common plane facing the other denture base,each flat surface being disposed over an area substantiallycorresponding to that previously covered by at least the first andsecond natural molars on a respective side of the mouth of the patient,said one denture base including a downwardly facing transverse fulcrumon each side of said denture base, each fulcrum being located within thespace previously occupied by the bicuspid teeth of the patient, theother denture base including a pair of elongated laterally spaced ridgeslying substantially in the common plane, each ridge extending for adistance substantially equal to that previously covered by at least thefirst and second natural molars on a respective side of the mouth of thepatient, each ridge also being continuous for a distance extending fromone side to the other of such fulcrum.

14. A prosthodontic masticatory system for an edentulous patient, thesystem comprising a lower denture base adapted to rest on the gum tissueoverlying the mandible of the patient, and an upper denture base adaptedto bear against the gum tissue overlying the maxilla of the patient, oneof the denture bases including a pair of elongated, laterally spacedflat surfaces lying in a common plane facing the other denture base,each flat surface being disposed over an area substantiallycorresponding to that previously covered by at least the first andsecond natural molars on a respective side of the mouth of the patient,said one denture base including a downwardly facing transverse fulcrumon each side of said denture base, the fulcrums being parallel and eachfulcrum being located within the space previously occupied by thebicuspid teeth of the patient the other denture base including a pair ofelongated laterally spaced ridges lying substantially in the commonplane, each rid e extending for a distance substantially equal to thatprevious y covered by at least the first and second natural molars on arespective side of the mouth of the patient.

15. A prosthodontic masticatory system for an edentulous patient, thesystem comprising a lower denture base adapted to rest on the gum tissueoverlying the mandible of the patient, and an upper denture adapted tobear against the gum tissue overlying the maxilla of the patient, one ofthe denture bases including a pair of elongated, laterally spaced flatsurfaces lying in a common plane facing the other denture base, eachflat surface being disposed over an area substantially corresponding tothat previously covered by at least the first and second natural molarson a respective side of the mouth of the patient, the other denture baseincluding a pair of elongated laterally spaced ridges lyingsubstantially in the common plane, each ridge extending for a distancesubstantially equal to that previously covered by at least the first andsecond natural molars on a respective side of the mouth of the patient,the biting edges of the upper lateral incisors and upper cuspids of oneof the denture bases being spaced above the common plane to preventprotrusive contact.

16. A prosthodontic masticatory system for an edentulous patient, thesystem comprising a lower denture base adapted to rest on the gum tissueoverlying the mandible of the patient, and an upper denture base adaptedto bear against the gum tissue overlying the maxilla of the patient, oneof the denture bases including a pair of elongated, laterally spacedflat surfaces lying in a common plane facing the other denture base,each flat surface being disposed over an area substantiallycorresponding to that previously covered by at least the first andsecond natural molars on a respective side of the mouth of the patient,the other denture base including a pair of elongated laterally spacedridges lying substantially in the common plane, each ridge extending fora distance substantially equal to that previously covered by at leastthe first and second natural molars on a respective side of the mouth ofthe patient, the lower anterior teeth on one of said denture bases beingdisposed below the common plane.

"H050 UNITED STATES PATENT OFFICE CERTIFIQAE 9F (:ORRECTIQN Patent3,638,309 Dated February 1, 11972 Inventor( s) John Po Frush It iscertified that error'appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Col, 2 line 5, "becomes" should read -become--. Col, 2 line ,5 7, "formplastie" should read "from plastic--. Col, 5, line 15, "intercept shouldread --intercepts--.

C010 5, line 34, "he dehtisiz' should read --the dentist--.

Col 6, line 45 "interior portions" should read --anterior portions- Col,6, line 46, "an' the" should read -and the--. Col, 7, line 42 thelateral" should read -the upper lateral". Col, 8, line 14,"itermaxillry" should read --'-ihtermaxillary--.

Col, 9, line 56 (Claim 13) "such" should read =--=each--.

Col. 10, line 24 (Claim 15) "denture adapted" should read denture baseadapted.

Signed and sealed this 27th day of June 1 972 (SEAL) Attest:

- EDWARD M.FLETGHER,JR, ROBERT GOTTSGHALK Attesting Officer Commissionerof Patents

1. A prosthodontic masticatory system for an edentulous patient, thesystem comprising a lower denture base adapted to rest on the gum tissueoverlying the mandible of the patient, and an upper denture base adaptedto bear against the gum tissue covering the maxilla of the patient, oneof the denture bases including at least one elongated portion having aflat surface facing the other denture and extending over an areasubstantially corresponding to that previously covered by at least thefirst and second natural molars, the other denture base including anelongated ridge extending for a distance at least equal to thatpreviously covered by the span between the mesial edge of the firstmolar and the distal edge of the second molar, the ridge projectingtoward the said flat surface to form a biting edge which lies insubstantially the same plane as the flat surface when the denture basesare held in centric contact.
 2. A system according to claim 1 whichincludes a first flat surface on one side of one of the denture bases,and a second flat surface on the opposite side of the denture facing theother denture, the first and second flat surfaces lying in a common flatplane, and a transverse ridge adjacent to each of the flat surfaces andextending toward the other denture base, each transverse ridge lyingwithin the space previously occupied by the natural bicuspid teeth ofthe patient, and laterally spaced elongated ridges on the said otherdenture each projected toward a respective flat surface to form bitingedges which lie in substantially the same plane as the flat surface whenthe denture bases are held in centric contact.
 3. A system according toclaim 2 in which the two flat surfaces are on the upper denture, and thebiting edges are on the lower denture.
 4. A prosthodontic masticatorysystem for an edentulous patient, the system comprising a lower denturebase adapted to rest on the gum tissue overlying the mandible of thepatient, and an upper denture base adapted to bear against the gumtissue overlying the maxilla of the patient, one of the denture basesincluding a pair of elongated, laterally spaced substantially continuousflat surfaces lying in a common plane facing the other denture base,each flat surface being disposed over an area substantiallycorresponding to that previously covered by at least the first andsecond natural molars on a respective side of the moutH of the patient,the other denture base including a pair of substantially continuouselongated laterally spaced flat ridges lying substantially in the commonplane, each ridge extending for a distance substantially equal to thatpreviously covered by at least the first and second natural molars on arespective side of the mouth of the patient.
 5. A system according toclaim 4 in which the common plane is substantially parallel to atransverse axis passing through the temperomandibular joint of thepatient.
 6. A system according to claim 5 in which the common planepasses substantially through the incisal edge of the upper centralincisor teeth of the upper denture.
 7. A system according to claim 5 inwhich the common plane passes through the upper portion of theretromolar pads of the patient.
 8. A system according to claim 6 inwhich the common plane passes through the upper portion of theretromolar pads.
 9. A system according to claim 4 in which the denturebase with the flat surfaces includes a downwardly facing transversefulcrum on each side of the said denture, each fulcrum being locatedwithin the space previously occupied by the bicuspid teeth of thepatient.
 10. A system according to claim 4 in which the incisal edges ofthe lower central incisors are spaced below the common plane.
 11. Asystem according to claim 10 in which the lower central incisors arebehind the upper central incisors to form an underbite.
 12. The systemaccording to claim 4 in which each ridge also extends for a distancesubstantially equal to that previously occupied by the bicuspid teeth ofthe patient.
 13. A prosthodontic masticatory system for an edentulouspatient, the system comprising a lower denture base adapted to rest onthe gum tissue overlying the mandible of the patient, and an upperdenture base adapted to bear against the gum tissue overlying themaxilla of the patient, one of the denture bases including a pair ofelongated, laterally spaced flat surfaces lying in a common plane facingthe other denture base, each flat surface being disposed over an areasubstantially corresponding to that previously covered by at least thefirst and second natural molars on a respective side of the mouth of thepatient, said one denture base including a downwardly facing transversefulcrum on each side of said denture base, each fulcrum being locatedwithin the space previously occupied by the bicuspid teeth of thepatient, the other denture base including a pair of elongated laterallyspaced ridges lying substantially in the common plane, each ridgeextending for a distance substantially equal to that previously coveredby at least the first and second natural molars on a respective side ofthe mouth of the patient, each ridge also being continuous for adistance extending from one side to the other of such fulcrum.
 14. Aprosthodontic masticatory system for an edentulous patient, the systemcomprising a lower denture base adapted to rest on the gum tissueoverlying the mandible of the patient, and an upper denture base adaptedto bear against the gum tissue overlying the maxilla of the patient, oneof the denture bases including a pair of elongated, laterally spacedflat surfaces lying in a common plane facing the other denture base,each flat surface being disposed over an area substantiallycorresponding to that previously covered by at least the first andsecond natural molars on a respective side of the mouth of the patient,said one denture base including a downwardly facing transverse fulcrumon each side of said denture base, the fulcrums being parallel and eachfulcrum being located within the space previously occupied by thebicuspid teeth of the patient the other denture base including a pair ofelongated laterally spaced ridges lying substantially in the commonplane, each ridge extending for a distance substantially equal to thatpreviously covered by at least the first and second natural molars on arespective side of the mouth of the patient.
 15. A prosthodonticmasticatory system for an edentulous patient, the system comprising alower denture base adapted to rest on the gum tissue overlying themandible of the patient, and an upper denture adapted to bear againstthe gum tissue overlying the maxilla of the patient, one of the denturebases including a pair of elongated, laterally spaced flat surfaceslying in a common plane facing the other denture base, each flat surfacebeing disposed over an area substantially corresponding to thatpreviously covered by at least the first and second natural molars on arespective side of the mouth of the patient, the other denture baseincluding a pair of elongated laterally spaced ridges lyingsubstantially in the common plane, each ridge extending for a distancesubstantially equal to that previously covered by at least the first andsecond natural molars on a respective side of the mouth of the patient,the biting edges of the upper lateral incisors and upper cuspids of oneof the denture bases being spaced above the common plane to preventprotrusive contact.
 16. A prosthodontic masticatory system for anedentulous patient, the system comprising a lower denture base adaptedto rest on the gum tissue overlying the mandible of the patient, and anupper denture base adapted to bear against the gum tissue overlying themaxilla of the patient, one of the denture bases including a pair ofelongated, laterally spaced flat surfaces lying in a common plane facingthe other denture base, each flat surface being disposed over an areasubstantially corresponding to that previously covered by at least thefirst and second natural molars on a respective side of the mouth of thepatient, the other denture base including a pair of elongated laterallyspaced ridges lying substantially in the common plane, each ridgeextending for a distance substantially equal to that previously coveredby at least the first and second natural molars on a respective side ofthe mouth of the patient, the lower anterior teeth on one of saiddenture bases being disposed below the common plane.